2 Answers
2

Get the right crush

This is the single most important thing to prevent a stuck sparge. Read the HomebrewTalk's wiki page on evaluating the crush. An ideal milling breaks the internal bits of grain into a coarse powder while leaving the bulk of the husks intact. It is the husks that do the most to set up a good filter.

Use a good manifold design

A large area covered by the manifold or pick-up, spaced evenly across the bed. A few, or a single, pick-up may lead to channeling, which compacts the grain bed. John Palmer covers this topic in his book How to Brew. His findings are the result of experiments he designed with fish tanks and dyed water.

Other things

Sparge slowly Take at least 30 minutes to rinse the grainbed.

Mash out Raising the mash temperature (168°F) not only stops enzymatic reactions, it makes the mash liquid flow more easily.

Keep the grainbed wet Always have an inch or two of water above the grainbed. If you let sparge water run too low the top may compress.

Rice hulls Available at most any LHBS, they add no flavor and increase the filtering capability of the grainbed. After you crush, mix the rice hulls into the grain.

One thing I have noticed with some of the recipe kits is that they don't always separate the adjuncts from the grain. Running flaked maize, wheat or oats through a mill is a guaranteed stuck sparge. Make sure that the more non-grain ingredients in the recipe the more attention you pay to volume, mash thickness, sparge temperature and flow rates. I think its mentally less frustrating to deal with if you know from the recipe that the probability of getting stuck is higher. Rice hulls are a must, get a big bag and keep them around.

Good point about thickness. More water in the tun helps prevnt the onset of a stuck sparge. By the time you finish vorlauf the grainbed should be well set and thickness matters less. I disagree about keeping rice hulls on hand. I've never had to use them. Never had a stuck sparge.
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Dean BrundageJan 13 '10 at 1:00